This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
There has been recent interest in replacing the conventional CCD (charge coupled device) photosensor with a two-dimensional array of small binary photosensors. Reference in this regard may be made to, for example, E. R. Fossum, What to do with Sub-Diffraction-Limit (SDL) Pixels? A Proposal for a Gigapixel Digital Film Sensor, Proc. of the 2005 IEEE Workshop on Charge-Coupled Devices and Advanced Image Sensors, Karuizawa, Japan, June 2005; L. Sbaiz, F. Yang, E. Charbon, S. Süsstrunk, M. Vetterli, The gigavision camera, Proc. of IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2009, p. 1093-1096; and L. Sbaiz, F. Yang, E. Charbon, S. Süsstrunk, M. Vetterli, Image reconstruction in gigavision camera, ICCV workshop OMNIVIS 2009.
Since the size of a binary photosensor is small compared to a traditional photosensor (e.g., a CCD photosensor), it can be reasonably assumed that a number of sensor elements (e.g., 16-256 elements) of a binary sensor array is smaller than that of the Airy disc (e.g., could be located within the size of an Airy disc). Thus, it is also reasonable to assume that the photon distribution on the sensor array can be modeled as a homogenous two-dimensional spatial Poisson process. The task then becomes to determine the intensity of light, given the output of binary sensor array.
A binary sensor is a simple sensor with only two states: initially zero, and after a number of detected photons exceeds some predetermined threshold, the state changes to one. Prior art binary sensor systems have considered only fixed threshold binary sensors.